Chronic granulomatous disease (CGD) is an inherited disorder in which phagocytic leukocytes fail to generate superoxide (O2-) and antimicrobial oxidants. Patients with CGD develop recurrent and often life-threatening infections due to catalase-positive microorganisms. We attempted to measure the production of nitric oxide and reactive oxygen species in polymorphonuclear neutrophils (PMNs) from patients with CGD using a flow cytometry technique. Venous blood was obtained from 5 male patients with X-linked CGD and from 10 healthy volunteers. The nitric oxide production by PMNs after phagocytosis was measured using diaminofluorescein-2 diacetate, a fluorescent indicator of intracellular nitric oxide production. After erythrocytes were hypotonically lysed, the cell pellet was applied to a cytofluorometer. Although the production of hydrogen peroxide by PMNs from patients with CGD was almost absent, nitric oxide production was detected at nearly half the level as was seen in the PMNs from healthy volunteers (CGD vs. healthy volunteers=140.1±28.6 vs. 256.4±10.3, mean fluorescence intensity; P<0.01). In conclusion, we demonstrated that human PMNs produces nitric oxide after phagocytic stimulation. Also nitric oxide production after phagocytic stimulation by PMNs of patients with CGD is observed although its amount is lower than that observed on healthy control. Despite the fact that CGD patients cannot produce H2O2 which is essential for intracellular bacteriocidal process after phagocytosis, our data suggested that the phylactic effect in PMNs induced by nitric oxide could be at least partially related to the survival of patients with CGD.